In 1901, a dentist from Massachusetts went to Colorado Springs, Colorado, to begin his practice. There, he encountered people who had dark brown stains on their teeth—but no sign of tooth decay.
He spent years trying to understand the phenomenon, but he died before the answer was revealed, decades later.
“They found that these people had brown teeth but very few cavities due to very high levels of fluoride naturally occurring in the water,” says UNC pediatric dentist Tim Wright, DDS. “The genesis of community water fluoridation was realizing that at a lesser amount of fluoride, there would be a reduction of cavities without the problems of the stain.”
In 1945, Grand Rapids, Michigan, became the first city to add fluoride to the drinking water, and 11 years later, researchers there reported that dental caries, or spots of tooth decay that typically become cavities, in children had dropped by more than 60 percent. Other areas continued to add fluoride to the water, with similar results, and the Centers for Disease Control and Prevention named community water fluoridation one of the 10 great public health achievements of the 20th century.
Fluoride is now a common ingredient in dental products such as toothpaste and mouthwash. That has led to questions about whether it’s still needed in water, and whether it can cause health problems.
Dr. Wright answers some commonly asked questions about fluoride.
What is fluoride?
Fluorine is an element that occurs naturally and is on the periodic table. When salts from this element are combined with minerals found in soil or rocks, fluoride is created.
“It’s the 13th most common element in the earth’s crust, so it occurs naturally in many water systems,” Dr. Wright says. “It can also be in the air or in foods,” with trace elements found in tea, coffee, some produce and fish, and products manufactured with fluoridated water.
Fluoride is also added to dental products—toothpaste, rinses, varnishes and dental floss.
How does fluoride help teeth?
Tooth decay occurs when bacteria in the mouth produce acid, which dissolves a tooth’s enamel and then the tooth itself. Sugary foods and beverages, as well as acidic foods and beverages, such as carbonated drinks and ultraprocessed foods, can increase the amount of acid in the mouth.
“Fluoride does multiple things to counteract tooth decay,” Dr. Wright says. “Fluoride binds to the enamel of the tooth and counteracts the damage from acid. It can help heal cavity formation and attract more enamel, ultimately making the enamel more acid-resistant.”
While many studies have focused on the benefits of fluoride for children and their developing teeth, Dr. Wright says that fluoride is important at any age.
“The process is the same, whether you’re 6 or 60—adults have enamel and can get caries. Adults are prone to caries at the roots that can become exposed with age, and those caries can be a real challenge for placing fillings,” he says. “When we look at the lifetime outcome of dental disease, people who spent more time in communities with fluoridated water had less dental disease than those who didn’t spend time in those communities.”
What are the risks associated with fluoride?
Ingesting too much fluoride can cause fluorosis. Symptoms of mild dental fluorosis are white flecks or spots on the teeth; with more severe fluorosis, some of the spots might be brown. Dental fluorosis may not respond to traditional whitening treatments.
When you ingest fluoride, some is absorbed by the teeth, but the majority goes into the bones or is excreted through urine. Long-term, excess consumption of high doses of fluoride could lead to skeletal fluorosis, which can cause bone and joint pain, but that is extremely rare in the United States.
Traditionally, dental caries and cavities are associated with a child having to miss days of school to go to the dentist, so prevention of tooth decay was linked to better school attendance. However, in recent years, some people and organizations have questioned whether fluoride could affect IQ or test scores, or raise the risk of attention-deficit/hyperactivity disorder.
“These aren’t things you can do randomized control studies on, so it’s about looking at community levels—one with fluoridated water, one with no added fluoride,” Dr. Wright says. “A study out of Sweden comparing natural to community fluoridation reported no relationship with fluoride and ADHD, changes in IQ or any measure of intellectual functioning.”
In 2024, a federal judge in California ordered the U.S. Environmental Protection Agency to strengthen regulations for fluoride in drinking water, citing a report from the U.S. Department of Health and Human Services’ National Toxicology Program that “higher” exposure levels of fluoride in the water (at or above 1.5 milligrams per liter) are associated with reduced IQ in children, based on a review of published scientific literature. The current recommended level of fluoride in public water is 0.7 milligrams per liter; the report noted that there was “insufficient data” on whether that fluoride level had a negative effect on IQ.
“The California ruling appears to be based on two times the level of community water fluoridation,” Dr. Wright says. “If I took two or three times the recommended dose of Tylenol or Motrin every day, I would expect negative outcomes from that, too. They have extrapolated beyond the data to say that if it’s harmful at higher doses, we shouldn’t use it at all.”
How can I tell how much fluoride I’m exposed to?
Risks associated with fluoride increase as you consume more fluoride. It is not easy to determine how much fluoride a person consumes, but Dr. Wright says that guidelines around levels in the water and in dental products were designed to ensure that people get an amount that could protect their teeth without any negative effects.
“The American Academy of Pediatrics and the American Academy of Pediatric Dentistry recommend fluoridated water at 0.7 parts per million,” Dr. Wright says. “That level is considered low-dose, low-risk but there are still good outcomes for preventing cavities. Sips of water flow over the tooth surface and make the tooth more resistant to decay.”
The current EPA enforceable standard is that fluoride cannot exceed 4 milligrams per liter, with a recommendation that it not exceed 2. According to the CDC, about 63 percent of the U.S. population has community fluoridated water, but each community’s precise fluoride level will vary. To find out how much fluoride is in your water, you can contact your local water provider. If you have well water, you may have to take a sample to your local health department to see how much fluoride naturally occurs.
A 2023 CDC report found that in 4,080 community water systems reporting data, water was safely fluoridated 99.99 percent of the time from 2016 to 2021 (below the 2 milligrams per liter recommendation) and that most people on those water systems were getting 0.7 milligrams per liter most of the time. The report raised concerns that some of these communities’ fluoride levels were actually below 0.7, meaning they may not be getting the full benefits of fluoridation. This report did not include data from all fluoridated water systems.
What about fluoride in toothpaste?
Our exposure to fluoride comes from a variety of sources, including dental products, according to Dr. Wright, which is why it is important to help young children when they brush their teeth.
“Most people use fluoridated toothpaste, so their exposure to fluoride depends on how much toothpaste is used, which is why it needs to be used in appropriate amounts and kids need to be encouraged not to eat it,” Dr. Wright says. “Our current guidelines suggest that kids ages 0 to 3 should have toothpaste the size of a grain of rice on their brush, in case they consume most of it. Over the age of 3, kids should use a pea-size amount, a very small dab. Adults can use more because they’re better at spitting out toothpaste, rather than swallowing it.”
Dr. Wright says that fluoride does need time to adhere to teeth, so don’t rinse with water after using a dental product with fluoride.
The American Dental Association recommends professionally applied fluoride as part of a dental visit, but the strength of the varnish, rinse, gel or foam depends on the patient’s age.
What would be the impact of removing fluoride from drinking water?
When the benefits of community water fluoridation were discovered, fluoride wasn’t an ingredient in toothpaste. Now it is, and some groups advocate removing it from community water supplies to reduce the risk that too much fluoride would be consumed.
“Some communities, having removed fluoride from the water, have seen tooth decay rates go up,” Dr. Wright says. “We predict more cavities if fluoride is removed from the water, and more dental disease in populations across the board, including the elderly. We can’t say what percentage increase it would be—it probably wouldn’t be as high as 50 percent, but even a 10 percent increase would be significant.”
Dr. Wright says that because fluoride is a commonly occurring natural element, many communities would not be able to get to a zero level of fluoride in the water.
Most water filters do not remove fluoride from tap water. Bottled water does not typically contain fluoride, but Dr. Wright notes that plastic bottles contain microplastics, which have been linked with a variety of diseases, including cancer.
If you’re concerned about fluoride, Dr. Wright recommends talking to your or your child’s dentist, and to remember that while this topic may be in the headlines, it’s important to keep the bigger picture in mind.
“There are other opportunities to manage dental health, and one option is to be more vigilant about diet,” he says. “The average American diet is often not healthy, with lots of exposure to ingredients that the bacteria in the mouth consume to make cavities. Fluoride is just one piece of the puzzle in the health of a child.”
If you have questions about your child’s health, talk to your doctor. If you need a doctor, find one near you.